Network reliability can be improved by increasing the MTBF or reducing the MTTR. Faults caused by various factors are inevitable, so fault recovery technologies are important. The following reliability technologies are mainly used to reduce the MTTR and meet level 3 reliability requirements.
Reliability technologies fall into fault detection technologies and protection switching technologies.
Fault detection technologies focus on fault detection and diagnosis. Table 1 describes the fault detection technologies.
Technology |
Description |
Link |
|---|---|---|
Bidirectional Forwarding Detection (BFD) |
BFD is a unified detection mechanism independent of media and protocols, and is used to rapidly detect link faults and monitor IP connectivity. |
|
Device Link Detection Protocol (DLDP) |
DLDP monitors the link status of optical fibers or copper twisted-pairs. When a unidirectional link is detected, DLDP automatically shuts down or requests users to manually shut down the interface to prevent network faults. |
|
Monitor Link |
Monitor Link associates an uplink interface with a downlink interface and is used on networks where Layer 2 topology protocols are used. Monitor Link monitors a device uplink interface and triggers the downlink interface status change according to the uplink interface status, which triggers switching of a topology protocol on the downstream device. |
|
MAC swap |
MAC swap loopback allows the device to swap source and destination MAC addresses in the received Ethernet frame header and send the frame to the sender so that the link status between the two devices is monitored. |
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Ethernet in the First Mile (EFM) |
EFM monitors network faults and is for use on last-mile Ethernet access links to users on the network. EFM needs to be enabled on the two directly connected devices so that EFM can monitor the link between the two devices. |
|
Connectivity Fault Management (CFM) |
IEEE 802.1ag CFM and ITU-T Y.1731 are operation, administration, and maintenance (OAM) mechanisms on Layer 2 links based on Ethernet link detection and are used to detect link connectivity, check faults, and locate fault on Layer 2 networks. |
|
Y.1731 |
Protection switching technologies focus on network recovery, and backs up hardware, link, service information, and routing information and perform fast switching to ensure service continuity. Table 2 describes protection switching technologies.
Technology |
Description |
Link |
|---|---|---|
Virtual Router Redundancy Protocol (VRRP) |
VRRP is a fault-tolerant protocol that allows the device to provide the default link when the default becomes faulty on LANs with multicast or broadcast capabilities. VRRP prevents network interruptions caused by the fault of the single link. |
|
Smart Link |
Smart Link provides redundancy in dual-homing networking and fast convergence, and rapidly switches services to the standby link when the active link becomes faulty. |